People in the study who rated their health as poor or fair were significantly more likely to develop dementia later in life than those who reported being in good health, the study found.

The link was strongest among people who did not have any cognitive problems, where those who rated their health as poor were nearly twice as likely to develop dementia as those who rated their health as good, the researchers said.

"Having people rate their own health may be a simple tool for doctors to determine a person's risk of dementia, especially for people with no symptoms or memory problems," said study researcher Christophe Tzourio, of the University of Bordeaux 2 in France.

"We know that having a large social network and social activities are associated with a decreased risk of dementia," Tzourio said. "Therefore, it's possible that rating one's health as poor might be associated with behaviors that limit social interaction, and in turn, accelerate the dementia process."

Other studies have shown people who rate their own health as poor are more likely to develop or die from vascular diseases, such as heart attack or stroke, than people who rate their health as good.

Pass it on: People who rate their health as poor are at increased risk of dementia, a study says.